Liquid Seaweed Fertilizer

Your garden needs nourishment from time to time. The obvious choice would be to use fertilizers, but for small-scale gardeners, this can be wasteful.

Organic sources of enrichment usually take a while to break down and be accessible to the plants. In addition, most organic fertilizers are animal-based and release ammonia, which can make things a bit smelly. 

To overcome all these problems, one solution might be a liquid seaweed fertilizer. 

liquid seaweed fertilizer - kelp
Photo by Shane Stagner on Unsplash

What is Liquid Seaweed Fertilizer?

Liquid seaweed fertilizer is a natural fertilizer made from seaweed. It is mostly produced from kelp, a brown seaweed that grows to extensive lengths.

The kelp seaweed is decomposed and fermented in water to produce a nutrient-rich source that can be used to stimulate plant growth and yield. 

Liquid seaweed fertilizers are called biostimulants or biofertilizers. These are materials of organic origin that help to supplement plant growth by supplying extra nutrients.

Biostimulants are often considered the perfect nutrient supplement as unlike many other methods, it is an environmentally friendly method to increase plant growth and yield.

Benefits of using liquid seaweed fertilizer

The nature of kelp fertilizers gives it an upper hand over any chemical fertilizer in many ways:

  • Nutrient uptake by plants is found to be more efficient when seaweed fertilizer is used as the nutrients are made available to plants in chelated, or easily absorbable, forms. This is also due to the manufacturing process of seaweed fertilizer, which involves breaking down the nutrients in order to make them more easily absorbed.
  • Kelp also contains alginate, a compound present in its cell walls that allows it to withstand tidal forces. When this is applied to soil, it helps bind soil particles together and improve the soil structure. This helps improve water and air movement through the soil, as well as acting as a soil conditioner.
  • Chemical fertilizers often render active microbial and animal life inactive, losing functions essential to the soil. On the other hand, seaweed fertilizers promote bacterial activity, enriching the soil and promoting healthier plant growth. 
  • Seaweed fertilizer has also been shown to improve the resilience of plants, aiding them to withstand insects and diseases. 
  • Leaching is a phenomenon where the nutrients in the soil are pushed out of reach for the plant roots making it difficult to absorb them. Seaweed fertilizer has microbes that bind the available nutrients together, hence preventing leaching. 
  • Kelp fertilizer also has naturally occurring growth stimulants. 
  • Seaweed is also known as an excellent compost activator.

Are seaweed based fertilizers more eco-friendly? 

Chemical fertilizers cause waterway pollution, increased air pollution, ocean acidification, and the mineral depletion of soil.

As seaweed fertilizers are derived from a plant source, they are organic and pose significantly less threat to the environment. They also have no chemical ingredients in them.

Provided they are sustainably harvested, seaweed is a renewable resource that naturally grows in abundance. Additionally, most liquid seaweed fertilizers are produced in an environmentally friendly method.

What does liquid seaweed fertilizer contain? 

It is a storehouse of minerals, amino acids, and enzymes. 

Although the main nutrients nitrogen, phosphorus and potassium, are not available in large amounts unlike other fertilizers, the amount that is present is readily available to the plants. Kelp fertilizer also contains trace elements that are essential for plant growth like magnesium and zinc.

Seaweed fertilizers also contain plant hormones like auxins, cytokinins, and betains, which are essential to plant health. The enzymes that are formed with the help of the nutrients present in seaweed fertilizers also help plants to produce their own hormones. 

How do you make liquid fertilizer from seaweed?

If you live near a beach, making your seaweed fertilizer is extremely easy and can be greatly beneficial to your plants. Here are the steps:

1. Collect seaweed from beaches in a container (check the rules for seaweed collection in your local area first). 

2. Bring the container home and rinse the seaweed to remove any sand.

3. Put the seaweed in a container and submerge it in water.

4. Close the lid and keep the container in a warm spot.

The seaweed will take anywhere from a few weeks to months, depending on the weather where you live, to decompose enough to form the liquid seaweed fertilizer.

Using the kelp fertilizer for your plants

As liquid seaweed fertilizers are very strong, they need to be diluted before use. The general dilution rule for houseplants is a ratio of 1:50 seaweed fertilizer to the water. 

The most efficient method of using this fertilizer is to do a foliar spray by spraying it onto the leaves. It is 8 to 20 times more effective when sprayed directly onto the leaves, rather than being applied to the root zone. Also, it has also been found that leaf pest attacks are lesser after foliar application.

It is recommended to spray the fertilizer onto the leaves as a fine mist until it begins to drip off. 

For more details on indoor gardening, please check our guide on how to grow herbs and vegetables in a small space.

When do I apply liquid seaweed fertilizer?

It is best to apply this fertilizer after the plants have an average of at least 3 leaves when they are actively growing. This is usually in spring or summer.

You can also spray the root ball with seaweed fertilizer to prevent transplant shock when repotting your plants. Before planting, you can soak your seeds overnight in it or spray after planting to see improved seed germination. If cuttings are placed in a liquid seaweed fertilizer solution, they start producing roots sooner.

Additionally, if applied 10 days before harvesting fruits and vegetables, it can also help to extend their shelf life.

Buying organic fertilizer

If you don’t live in an area with access to a beach, you can also buy quality seaweed fertilizer online.

Neptune’s Harvest Organic Hydrolized Fish & Seaweed fertilizer, Organic Hydrolysed Fish and Seaweed blend, and GS Plant Foods Organic Liquid Kelp Plant Fertilizer are high-rated organic fertilizers available on Amazon. 

As the trend of switching to sustainable alternatives is gaining momentum, this is the perfect time to try this organic fertilizer and enrich both your vegetable garden and your indoor plants. 


How can you find out if a beach in your area allows for seaweed to be collected for home use as a fertilizer?

You have to check with your local guidelines. Collecting seaweed is illegal in some parts of the world in order to help protect local ecosystems.

What is Norwegian kelp?

Norwegian kelp, also known as Ascophyllum nodosum, is a seaweed that only grows in the northern Atlantic Ocean and is one of the most widely tested kelps for use in agriculture.

Are seaweed and kelp the same thing?

Seaweed is a broad term for thousands of species of marine algae, while kelp is a specific subcategory.

Is kelp a plant or algae?

Kelp is not a plant but rather brown algae that live in cool waters close to the shore.


Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *